Tooling apparatus for modifying nuclear reactors

ABSTRACT

A remotely controlled tooling apparatus is disclosed for supporting and selectively disposing a tool with respect to a workpiece illustratively taking the form of a core barrel of a nuclear reactor. Illustratively, a core barrel is of a substantially cylindrical configuration and has a plurality of flow holes disposed therethrough. The remotely controlled apparatus comprises a tool carriage, a support table carried thereby for receiving the tool, a strongback assembly for supporting and guiding the tool carriage with respect to the core barrel, and a pair of clamps affixed to the strongback assembly for engaging the core barrel for suspending the strongback assembly upon the core barrel. The tool carriage and its support table carried thereby are selectively disposed with respect to the core barrel, whereby the tool may be engaged and disengaged with and from the core barrel. In an illustraitive embodiment of this invention, the tool takes the form of an arm for releasably holding a plug to the inserted into a selected one of the existing flow holes.

BACKGROUND OF THE INVENTION

This invention relates to apparatus for modifying nuclear reactors and,more particularly, to an electromechanical apparatus for remotelylocating, measuring and inserting plugs within coolant flow holes of acore barrel of a nuclear reactor.

A nuclear reactor 10, typical of the prior art, is shown in FIG. 1A asincluding a reactor vessel 16 into which is pumped a coolant fluidthrough an inlet 20 and, after cooling the reactor, to be dischargedthrough an outlet 22. A core barrel 14 is disposed within the reactorvessel 16 and comprises a top former plate 12 and a baffle plate 32. Asillustrated in FIG. 1A, the coolant flow is directed through an existingflow hole 26 downwardly along a path 34b and through an opening formedbetween the bottom of the baffle plate 32 and a lower core plate 18. Aplurality of nuclear fuel rod assemblies 24, one of which is illustratedin FIG. 1A, is disposed within the core barrel 14. The coolant fluid isalso directed downwardly along a path 34a and upwardly, as shown in FIG.1A, through a plurality of openings 14a-14e formed within the bottom ofthe core barrel 14. Subsequently, the fluid directed into the corebarrel 14 is directed upwardly through a plurality of openings 19a to19d within a lower core plate 18 and, thereafter, directed about theplurality of nuclear fuel rod assemblies 24, thereby, removing heattherefrom.

In a nuclear reactor 10 of the downflow design, as shown in FIG. 1A,damage has been sustained to the fuel rods of the assemblies 24.Analysis indicates that the coolant flow, as directed along the path 34band discharged through that opening formed between the baffle plate 32and the lower core plate 18, impinges against and damages the fuel rods.To prevent nuclear fuel rod damage, it is proposed to convert a nuclearreactor from a downflow-type nuclear reactor 10, as illustrated in FIG.1A, to an upflow-type reactor 10', as illustrated in FIG. 1B. Referringnow to FIG. 1B, this conversion requires: (1) machining a plurality ofnew flow holes 28 within the top former plate 12, one such hole 28 beingillustrated in FIG. 1B, and (2) plugging the existing flow holes 26 withplugs, one such plug 30 being illustrated in FIG. 1B. (Need adescription of or reference to a description of the plugs 30?). Thenumber of holes 26 and their location within the vertical wall of thecore barrel 14 depends upon the particular type of nuclear reactor 10,i.e., whether the nuclear reactor 10 includes 2, 3 or 4 loops.

Referring now to FIG. 2, a core barrel 14 is illustrated as beingsubmerged in canal water 40 filling a refueling canal 36 formed betweencanal walls 38a and 38b. The core barrel 14 includes a flange 66disposed about its top-most edge. Due to the proximity of the corebarrel flange 66 to the canal walls 38, the upflow conversion needs tobe performed on the core barrel 14 while it is immersed within therefueling canal 36. As will be explained below, the apparatus of thisinvention serves to locate and measure the existing holes 26 within thecore barrel 14, before inserting plugs 30 therein. It is imperative thatthese tasks be performed remotely in that there exists a high level ofradiation adjacent to the core barrel 14 and the canal water 40.

SUMMARY OF THE INVENTION

The remotely controlled tooling apparatus of this invention provides asystem for supporting and selectively disposing a tool with respect to aworkpiece illustratively taking the form of a core barrel of a nuclearreactor. Illustratively, a core barrel is of a substantially cylindricalconfiguration and has a plurality of flow holes disposed therethrough.The remotely controlled apparatus comprises a tool carriage assembly forreceiving the tool, a strongback assembly for supporting and guiding thetool carriage with respect to the core barrel, and a pair of clampsaffixed to the strongback assembly for engaging the core barrel forsuspending the strongback assembly along a first dimension substantiallyparallel to an axis of the core barrel. A first drive motor is mountedon the strongback assembly and is coupled to the tool carriage forselectively driving the tool carriage along the first dimension.Further, a support table is movably mounted on the tool carriage alongan arcuate path corresponding to the cylindrical configuration of thecore barrel. A second drive motor is mounted on the tool carriage andcoupled to the support table for selectively driving the support tablealong the arcuate path. A third drive motor is mounted on the supporttable and is coupled to the tool for selectively disposing the toolalong a second dimension aligned with respect to the radius of thecylindrical configuration, whereby the tool may be engaged anddisengaged with and from the core barrel. In an illustrative embodimentof this invention, the tool takes the form of an arm for releasablyholding a plug to be inserted into a selected one of the existing flowholes.

In a further aspect of this invention, there is included a sensor forsensing the location of a flow hole and a fourth drive motor mounted onthe support table for disposing the sensor along the second dimensionwith respect to the core barrel. Further, a sensor arm is coupled to thefourth drive motor for carrying and positioning the sensor with respectto a flow hole.

The core barrel includes a plurality of pointers disposed thereon in afixed relation with corresponding of the plurality of flow holes. Anindicator is mounted upon the tool carriage to permit alignment of theremotely controlled apparatus with respect to corresponding ones of theplurality of flow holes.

Further, the remotely controlled apparatus includes a first encodermounted on the tool carriage and coupled to the support table forproviding an output signal indicative of the relative movement betweensaid support table with respect to the indicator means along saidarcuate path, and a second encoder mounted on the support table andcoupled to the tool for providing an output signal indicative of themovement imparted to the tool by the third drive means along the seconddimension.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter of the invention, it isbelieved that the invention will be better understood from the followingdescription taken in conjunction with the accompanying drawings,wherein:

FIGS. 1A and 1B are respectively side, sectioned views of nuclear fuelreactors of a downflow design and of an upflow design, respectively;

FIGS. 2A and 2B are respectively a perspective view of a core barrel ofthe nuclear reactor shown in FIGS. 1A and 1B as immersed in canal waterand the locating, measuring and insertion apparatus of this invention asincluding a strongback assembly and a tool carriage assembly disposedfor rectilinear motion along the strongback assembly, and an explodedview of the tool carriage assembly;

FIG. 3A, 3B and 3C are respectively detailed front, side and top viewsof the strongback assembly as generally shown in FIG. 2, FIG. 3D is apartial, broken away, side view of a clamp for mounting the strongbackassembly upon the core barrel, and FIG. 3E is a plan view of a templatedisposed upon a flange of the core barrel for accurately positioning thestrongback assembly with respect to the existent, coolant flow holesdisposed within the core barrel;

FIG. 4A is a plan view of the tool carriage assembly as mounted upon thestrongback, showing its relationship to the core barrel, and FIGS. 4Band 4C are respectively a sectioned side view of the tool carriageassembly and a sectioned plan view of the tool carriage assembly astaken along lines 4c--4c of FIG. 4B;

FIGS. 5A and 5B are respectively a front, partially broken away view anda side, partially broken away view of a radial drive assembly that ismounted upon the tool carriage assembly, as shown in FIGS. 4A, 4B and4C, and FIG. 5C is a front view of the plug arm as rectilinearly drivenand supported by the radial drive assembly of FIGS. 5A and 5B; and

FIG. 6 is a functional block diagram of the elements for energizing andcontrolling the various functions of the tool carriage assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings and, in particular, to FIG. 2, there isshown a plug installation tool system 50 in accordance with theteachings of this invention to install plugs 30 in a plurality ofexisting flow holes 26 as disposed about the periphery of the corebarrel 14. The plug installation tool system 50 includes a strongbackassembly 52 and a tool carriage assembly 54 mounted upon the strongbackassembly 52 for rectilinear motion therealong in a vertical direction,as shown in FIG. 2. The strongback assembly 52 includes a pair of claps64a and 64b of a C-type configuration to fit over the flange 66 of thecore barrel 14. A hydraulic clamp 72 is used to positively secure theclamps 64a and 64b and, thus, the strongback assembly 52 with respect tothe core barrel 14. As illlustrated in the expanded portion of FIG. 2,the tool carriage assembly 54 includes a plug arm 154 for carrying andinserting a plug 30 accurately within one of the existing flow holes 26.A plug arm drive motor 158 drives the plug arm 154 and its plug 30 in arectilinear motion as indicated by the arrow 62. Similarly, acircumferential drive motor 140 drives the plug arm 154 in a rectilinearmotion as indicated by the arrow 60, whereby the plug 30 may beaccurately aligned with respect to one of the existing flow holes 26,before the plug arm drive motor 158 is energized to drive the plug 30into the existing flow holes 26.

The existing flow holes 26 are disposed about the periphery of the corebarrel 14 and it is necessary to reposition the strongback assembly 52to permit the plugs 30 to be disposed in a next pair of existing flowholes 26, noting that the plug arm 154 may be moved right and left fromthe center of the strongback assembly 52. To this end, a temporary workbridge 42 is disposed over the refueling canal 36 and is movably drivenalong a pair of manipulator crane rails 46a and 46b whereby thetemporary work bridge 42 and, thus, the strongback assembly 52 may bepositioned selectively over the core barrel 14. A control panel isdisposed upon a work deck 44 of the temporary work bridge 42 to permitcontrol of the various functions of the plug installation tool system50. When it becomes necessary to move the strongback assembly 52 aboutthe periphery of the core barrel 14, the operator may readily position ahoist 49 directly over the strongback assembly 52 and, thereafter,attach the hoist cable to the strongback assembly 52, before actuatingthe hoist 49 to lift the strongback assembly 52. In this regard, thehoist 49 may be moved along its monorail 48 and the temporary workbridge 42 may be variously disposed over the core barrel 14.

Referring now to FIGS. 3A and 3B, there is provided a detail showing ofthe structure of the strongback assembly 52 and the manner in which thetool carriage assembly 54 is driven rectilinearly along the lengththereof. The strongback assembly 52 is comprised of lower, middle andtop weldments 52a, 52b and 52c, thus, permitting the assembly 52 to bedismantled for shipment and reassembled at the site of the core barrel14. Each weldment is comprised of four upright legs 92a, 92b, 92c and92d. The structural integrity of the strongback assembly 52 is assuredby a plurality of side braces 94 extending between the upright legs 92aand 92d, and legs 92b and 92c. In addition, back braces 98 are disposedbetween the upright legs 92d and 92c. The side and back braces 94 and 98are attached by welding to the upright legs 92 and reinforced by gussets96. A pair of Thomson rails 70a and 70b extend along the length of thestrongback assembly 52 for guiding and supporting the tool carriageassembly 54 for rectilinear movement therealong.

As shown in FIGS. 3A, 3B and 3C, a carriage hoist assembly 80 is mountedon top of the strongback assembly 52 for reeling in and out a hoistcable 82 connected at its remote end, as shown in FIG. 3A, to the toolcarriage assembly 54, whereby the carriage 54 may be lowered and raisedrespectively along the length of the strongback assembly 52. The hoistassembly 80 includes a cable drive motor 84 mounted upon the top of thestrongback assembly 52 and coupled by a gear mechanism 87 to drive apair of cable reels 86, as shown in FIGS. 3C. The cable 82 is woundabout the cable reel 86 and that the cable drive motor 84 is operativeto rotate in opposite directions to reel in and reel out the hoist cable82, whereby the carriage assembly 54 is respectively raised and loweredalong the length of the strongback assembly 52.

As shown in FIG. 3C, a pair of TV cameras 88a and 88b is disposed onopposite sides of the strongback assembly 52. In particular, each of thecameras 88a and 88b is mounted upon corresponding positioning mechanisms89a and 89b, whereby the cameras 88a and 88b may be disposed from afirst or retracted position, as shown in full line in FIG. 3C, to anextended, viewing position, as shown in dotted line in FIG. 3C. The TVcameras 88a and 88b serve to permit direct observation of the existingflow holes 26, the inserted plugs 30, and the surrounding surfaces ofthe core barrel 14.

Details of the clamps 64a and 64b and the manner in which the strongbackassembly 52 is mounted upon the core barrel 14 are shown in FIG. 3D. Theclamps 64a and 64b are securely affixed to the strongback assembly 52 asby bolting. Each of the clamps 64a and 64b includes a U-shaped recess102 for receiving therein the flange 66 of the core barrel 14. Therecess 102 is configured to provide a support surface 103 disposedsubstantially horizontal to provide a surface for supporting the weightof the clamps 64 and the strongback assembly 52 upon the flange 66 ofthe core barrel 14. As shown in FIG. 3D, the support surface 103 restson a bearing pad 104, which in turn rests on a hold down spring 100. Thehold down spring 100 is disposed between the bearing pad 104 and theupper surface of the flange 66. In addition, a pair of bearing pads 90and 106 are disposed on either side of the flange 66 to prevent damageto either the flange 66 or the clamps 64 disposed thereon. Asillustrated in FIG. 3D, the lateral dimensions of the recess 102, aswell as the spacers 90 and 106, permit a degree of freedom for movementof the clamps 64a and 64b with respect to the flange 66. A pair of legs118, of which one leg 118a is shown in FIG. 3D, is disposed on a lowerportion of the strongback assembly 52. At the end of each leg 118 isdisposed a rotatably mounted wheel 120 to permit circumferential motionof the strongback assembly 52 about the outer periphery of the corebarrel 14.

Referring now to both of FIGS. 3D and 3E, a template 112 is illustratedas comprised of four equal 90° sectors 112a, 112b, 112c and 112dconfigured and dimensioned to cover to entire circumference of theflange 66 of the core barrel 14. A plurality of, illustratively four,locating pins 110 is disposed 90° apart about the circumference of theflange 66 and serves to accurately position the template 112 withrespect to the core barrel 14 and its existing flow holes 26. As shownin FIG. 3D, a locating pin 110 is disposed in a close fittingrelationship within an opening 116 through the template 112. Asparticularly illustrated in FIG. 3E, a plurality of existing flow holes26a through 26s is disposed at varying angles about the circumference ofthe core barrel 14. In an illustrative embodiment of this invention, aplurality of pointers 122 is disposed along the periphery of the corebarrel 14, each pointer 122 accurately locating a pair of existing flowholes 26 disposed on either side of the pointer 122. For example, thepointer 122a is disposed midway between the existing flow holes 26a and26b. As will be explained later, if the strongback assembly 52 isaccurately disposed by the hoist 49 with respect to one of the pointers122, its position with respect to the corresponding pair of existingflow holes 26 is accurately determined. In an illustrative embodiment ofthis invention, the template 112 is made of a metal, illustratively of astainless steel, having dimensions of 4"×3"×0.25" thick.

Referring now to FIG. 4A, there is shown a plan view of the top of thestrongback assembly 52 and its clamps 64a and 64b, illustrating themanner in which the clamps 64a and 64b are disposed about the flange 66of the core barrel 14. An outer peripheral surface 108 of the flange 66is machined to close tolerance in the order of ±0.03 inch to provide areference surface against which the strongback assembly 52 is mounted.As a result, the radial distance from the strongback assembly 52 to thecore barrel 14 and its existing flow holes 26 is accurately established.Further, a jack support brace 74 is disposed between the clamps 64a and64b, with its opposite ends fixedly secured to corresponding one's ofthe clamps 64a and 64b. The hydraulic jack 72 is fixedly disposed at thecenter line of the jack support base 74. After the strongback assembly52 and its clamps 64a and 64b have been disposed upon the flange 66 ofthe core barrel 14, pressure is increased within the hydraulic jack 72,thereby disposing its piston 73 from its retracted position as shown infull line in FIG. 4A, to its extended position shown in dotted line inFIG. 4A, whereby the strongback assembly 52 is fixedly secured to thecore barrel 14.

Further, an indicator support brace 76 is likewise attached between theclamps 64a and 64b for centrally supporting an indicator 78. Asillustrated in FIG. 4A, the indicator 78 permits alignment with aselected one of the pointers 22 set on the template 112. In operation,the operator manipulates the hoist 49 to place the strongback assembly52 in a position such that its indicator 78 is aligned with a selectedone of the pointers 122. In this manner, the strongback assembly 52 and,in particular, its tool carriage assembly 54 is disposed in a knownrelationship with that pair of existing flow holes 26 disposed on eitherside of the pointer 122, as explained above.

As shown in FIGS. 3A and 3B, the tool carriage assembly 54 is mounted bythe Thomson rails 70a and 70b for rectilinear motion on the strongbackassembly 52. As shown in FIGS. 4A and 4C, a resolver 220 is mounted upona side bracket 126a to sense the relative movement of the tool carriageassembly 54 with respect to the strongback assembly 52 and, inparticular, to provide a train of pulses, each pulse indicative of aunits, linear movement. As particularly shown in FIG. 4A, the resolver220 includes a pinion gear 226 engaging a track 224 mounted on thestrongback assembly 52 by an angle support 222. The angle support 222and the track 224 extend the vertical length of the strongback assembly52. As the tool carriage assembly 54 moves rectilinearly along thelength of the strongback assembly 52, the pinion gear 226 meshing withthe track 224 causes the encoder 220 to provide the aforementioned trainof pulses.

In order to actuate the various hydraulic devices and electrical motorsincluded within the tool carriage assembly 54, it is necessary to runhydraulic cables 55 and electrical cables 56, as shown in FIG. 4A, fromthe top of the strongback assembly 52 to the tool carriage assembly 54,as generally illustrated in FIG. 3B. Thus, it is necessary to compensatefor the slack that may exist in the hydraulic cables 55 and electricalcables 56 as the tool carriage assembly 54 is moved up and down thestrongback assembly 52. To this end, a pair of counterweight pulleyassemblies 57a and 57b, as shown in FIG. 4A, receive the hydrauliccables 55 and electrical cables 56, and exert a downward force thereon,as illustrated in FIG. 3B. As illustrated in FIG. 4A, each of thecounterweight pulley assemblies 57 is mounted respectively upon a firstpair of vertical tracks 59a and 59b, and a second pair of verticaltracks 59a and 59c. In turn, each pair of the vertical tracks 59 isaffixed to the left or right side of the strongback assembly 52, asshown in FIG. 4A, and oriented to extend the length thereof, as shown inFIG. 3B. Further, the tool carriage assembly 54 includes a pair of sidebrackets 126a and 126b for respectively mounting a pair of guide members61a and 61b for directing the hydraulic cables 55 and electrical cables56 downwardly from the tool carriage assembly 54 to their counterweightpulley assemblies 57a and 57b.

Referring now to FIGS. 4B and 4C, the details of the tool carriageassembly 54 are shown. The carriage assembly 54 provides thecircumferential and radial drive systems for locating a plug 30 oppositeone of the existing flow holes 26 in the core barrel 14 and, thereafter,for inserting the plug 30 into an aligned existing flow holes 26. Asshown best in FIG. 4B, the tool carriage assembly 54 includes acircumferential table 136 that is driven rectilinearly along an actuatepath corresponding to the curvature of the flange 66 of the core barrel14. In particular, the circumferential table 136 is driven along a pairof curved upper and lower tracks 130a and 130b. Though not shown inFIGS. 4B and 4C, it is understood that a radial drive assembly 152 ismounted upon the table 136, as will be explained below with respect toFIGS. 5A and 5B.

As illustrated in FIGS. 4B and 4C, the tool carriage assembly 54includes a carriage frame weldment 4. The side brackets 126a and 126b isattached to either end of the carriage frame weldment 124. Asillustrated in FIG. 4B, the pair of upper and lower tracks 130a and 130bis mounted upon the carriage frame weldment 124. Further, a pair ofbearing brackets 134a and 134b is disposed at either end of the carriageframe weldment 24 for mounting a pair of Thomson bearings 132a and 132b.As specifically shown in FIG. 4A, the Thomson bearings 132a and 132breceive corresponding Thomson rails 70a and 70b, whereby the toolcarriage assembly 54 moves rectilinearly along the length of thestrongback assembly 52.

As particularly illustrated in FIG. 4B, the circumferential table 136includes a vertically disposed support member 138 upon which are mountedan upper pair of guide wheels 150a and a lower pair of guide wheels 150bfor respectively receiving the upper track 130a and the lower track130b. A track support 128 is affixed to the carriage frame weldment 124and mounts and upper and lower tracks 130a and 130b in positions toengage the pairs of guide wheels 130a and 130b, respectively. Further, arack 148 of a curved configuration similar to that of the upper andlower tracks 130a and 130b and the core barrel 14, is likewise mountedupon the track support 128. As shown in FIGS. 4B and 4C, acircumferential drive motor 140 and a circumferential encoder 142 aremounted upon the circumferential table 136 and include pinion gears 144and 146, respectively, each engaging the rack 148. The circumferentialencoder or resolver 142 provides feedback signals indicative of theposition of the circumferential table 136 and, in particular, the radialdrive assembly 152 mounted thereon with respect to the indicator 78 and,therefore, the corresponding pair of existing flow holes 26.

The radial drive assembly 152 that is fixedly secured to thecircumferential table 136 of the tool carriage assembly 54 is more fullyshown in FIGS. 5A and 5B. The radial drive system 152 includes a plugarm 154 for releasably carrying and inserting a plug 30 into an existingflow flow hole 26, and a probe arm 156 for carrying and variablypositioning a probe 178 which serves to located and to provide anindication indicative of the measurements of the existing flow holes 26.In an illustrative embodiment of the invention, the probe 178 may takethe form of an array of eddy current devices 179, as shown in FIG. 5A.In particular, four eddy current devices 179a, 179b, 179c and 179d areequally spaced from each other about the circumference of the probe 178,whereas a fifth eddy current device 179e is disposed along the axis ofthe probe 178. The axially disposed eddy current device 179e provides anelectrical signal indicative of the radial distance between the probe178 and the peripheral surface of the core barrel 14. Thecircumferential table 178 supporting the probe arm 156 and its probe 178may be scanned back and forth across the surface of the core barrel 14,while the output of the eddy current device is observed. When the outputof the eddy current device 179e reaches a maximum, there is anindication that the eddy current device 179e is partially aligned withthe vertical axis of a corresponding flow hole 26. It is furthernecessary to align the probe 178 with respect to the horizontal axis ofthe flow hole 26 by moving the tool carriage assembly 54 vertically withrespect to the flow hole 26 until a maximum output signal is derivedfrom the eddy current device 179e, indicating that the probe 178 isaligned with a horizontal axis passing through the center of thecorresponding flow hole 26. The probe 178 may be disposed in this mannerto an accuracy of approximately 0.10 inch with respect to the center ofa corresponding flow hole 26. After being so aligned, the radial driveassembly 152 is actuated to insert the probe 178 into the aligned,existing flow hole 26. Thereafter, the eddy current devices 179a, 179b,179c and 179d are used to more accurately position the probe 178 withrespect to its existing flow hole 26, as well as to measure the diameterof the hole 26. In particular, left and right eddy current devices 179band 179e, as well as top and bottom eddy current device 179a and 179c,are coupled together to provide difference and sum signals. In thealigning process, difference signals are obtained in order to preciselyposition the probe 178 with respect to the axis of the existing flowhole 26 to a tolerance of 1.5 mils. After being precisely aligned, theoutput signals of the corresponding eddy current devices 179 are summedto provide an accurate indication of the diameter of the aligned,existing flow hole 126.

As shown in FIG. 5A, the plug arm 154 is associated with a plug armdrive motor 158 and a plug arm resolver 196. The plug arm drive motor158 and the plug arm resolver 196 are supported upon a support frame 162comprised, as shown in FIGS. 5A and 5B, of a top plate 164a, side plates164b and 164d, and a bottom plate 164c. The bottom plate 164c is in turnaffixed to the circumferential table 136, as shown in FIG. 4B. Each ofthe plug arm drive motor 158 and the plug arm resolver 196 includes acorresponding pinion gear. The pinion gear 166 driven by the plug armdrive motor 158 is illustrated in FIG. 5A; the pinion gear for the plugarm resolver 196 is not illustrated in the drawings. Each of thesepinion gears engages a rack 171, coupled to drive the plug arm 154. Theplug arm resolver 196 provides electrical signals indicative of theprecise precision position of the plug arm 154. As shown in FIG. 5A,upper and lower pairs of guide wheels 168a and 168b are rotatablymounted upon the side plate 164d of the support frame 162. Upper andlower tracks 170a and 170b are affixedly attached to a plug arm slide173, as shown in FIGS. 5A and 5B. The plug arm slide 173 is in turnaffixed to and supports the plug arm 154 for rectilinear motion in theradial direction.

Similarly, there is provided a probe arm drive motor 160, shown in FIG.5A, and a probe arm resolver not illustrated. The probe arm drive motor160 has a pinion gear 172 and the probe arm resolver has a pinion; eachof these pinion gears engages a rack 175 affixed to a probe arm slide177. In turn, the probe arm slide 177 is affixed to the probe arm 156,whereby the probe arm 156 is rectilinearly driven in a radial directionand an output signal obtained from the probe arm resolver indicative ofthe precise position of the probe arm 156 with respect to the corebarrel 14. As illustrated in FIG. 5A, an upper pair of guide wheels 174aand a lower pair of guide wheels 174b are rotatably mounted upon theside plate 164b of the support frame 62. An upper track 176a and a lowertrack 176b are affixed to the probe arm slide 177 and are positioned toengage and to be mounted respectively upon the upper and lower pair ofguide wheels 174a and 174b.

The probe arm 156 has a pair of recesses 180a and 180b disposed oneither end for receiving the probe 178. Illustratively, the probe 178 isheld in its recess 180 by a pair of set screws 182; one pair of setscrews 182a is associated with the recess 180a, while a second pair ofset screws 182b is associated with the recess 180b.

Referring now to FIG. 5C, the plug arm 154 is shown in greater detail. Apair of recesses 184a and 184b is disposed within each end of the plugarm 154. A slide 186 is mounted with respect to the probe arm 154 forrectilinear motion along a horizontal direction, as shown in FIG. 5C.The slide 186 serves to grasp and retain a plug within one of therecesses 184. In FIG. 5C, the slide 186 is disposed to the left to thatposition as would retain a plug 30 within the recess 184b. It isunderstood that the slide could be disposed to the right, as seen inFIG. 5C, to retain a plug within the recess 184a. The slide 186 isprovided with a pair of curved, gripping surface 188a and 188b foreffecting a secure gripping of the plug 30, which is of a likeconfiguration. The slide 186 is rectilinearly driven by a double actinghydraulic cylinder 190. The hydraulic cylinder 190 drives a piston 191coupled to a clevis 192, which is in turn coupled by a drive bracket 194to move the slide 186 with a rectilinear movement.

In an illustrative embodiment of this invention, each of thecircumferential drive motor 140, the plug arm drive motor 158 and theprobe arm drive motor 160 may taken the form of a globe motormanufactured by TRW Company under their designation type BL 102 A818-10.The cable drive motor 84 may illustratively taken the form of thatservomotor manufactured by Electrocraft Corporation under theirdesignation 0670-07-021. The resolvers 142, 196, 198 and 220 may takethe form of those encoders as manufactured by Computer ConversionCorporation under their designation number NES 90-DBC-10-1.

Referring now to FIG. 6, there is shown a control circuit 200 forselectively energizing and controlling the various motors associatedwith the strongback assembly 52, its tool carriage assembly 54 and thehoist 49. Readily available 60 Hz alternating current voltage is appliedto a power supply 202 for providing a DC voltage output to a motorcontrolled circuit 204. The motor control circuit 204 includes aforward/reverse control 205, a jog switch 206 and a meter select switch208. The jog switch 206 is actuated to increase the voltage as appliedto the selected one of the drive motors 140, 158 and 160, whereby thecorresponding motor is driven at a greater speed. The operator disposesthe motor select switch 208 to any one of its three positions a, b and cto respectively energize one of the circumferential drive motor 140, theplug arm drive motor 158 and the probe arm drive motor 160. Similarly,the operator manipulates the forward/reverse control 205 to direct theselected motor in a forward or reverse direction. As illustrated by adash-line in FIG. 6, each of the aforementioned motors is mechanicallycoupled with a corresponding circumferential resolver 142, plug armresolver 196, and probe arm resolver 198. The output signals of theseresolvers 142, 196 and 198 are respectively indicative of the positioncircumferential table 136 and its radial drive assembly 52 with respectto the indicator 78, the plug arm 154 with respect to the machinedsurface 108 of the core barrel 14, and the probe arm 156 with respect tothe machined surface 108 of the core barrel 14. In turn, these signalsare applied to a resolver/display electronic circuit 210, which in turndisplays these signals upon corresponding display devices 212a, 212b and212c.

The alternating current voltage is also applied to a motor controller218 which in turn energizes the hoist motor, whereby the hoist cable 82and the tool carriage assembly 54 connected to an end thereof is drivenup and down the strongback assembly 52. The cable drive motor 84 is inturn coupled to the resolver 220 which provides an output signalindicative of the position of the tool carriage assembly 54, asexplained above; the output of the encoder 220 is applied to aresolver/display electronics 210 for providing a corresponding signal toa position display 212d indicative of the position of the tool carriageassembly 54 with respect to the strongback assembly 52.

As seen in FIG. 6, the eddy current sensor 178 is coupled to an eddycurrent signal conditioner 214 which in turn provides signals to displaydevices 216a and 216b. As explained above, the probe 178 includes thefive eddy current devices 179. The output signals of the five eddycurrent devices 179a, 179b, 179c, 179d and 179e are applied to an eddycurrent signal conditioner 214 to provide output signals to displaydevices 216a and 216b. Illustratively, the display device 216a providesan output corresponding to the eddy current sensor 179e indicative ofthe radial distance between its probe 178 and the outer peripheralsurface of the core barrel 14. In turn, the display device 216b providesselectively indications of the signal differences of the coupled eddycurrent devices 179b and 179e, and 179a and 179c, as well as the signalsums of the aforementioned eddy current sensors. As noted above, thedifference signals serve to precisely orient the probe 178 with respectto an existing flow hole 26, whereas the sum signals provide an accurateindication of the diameter of the aligned, existing flow hole 26. In anillustrative embodiment of this invention, the eddy current sensors 179ato d, and 179e may take the form, respectively, of the eddy currentsensors as manufactured by Kaman under their designations 2UB1 (KD 4000Series) and 3U1, and the signal conditioner 214 takes the form of thatcircuit manufactured by Kaman under their designation KD4056.

The method of installing a plug 30 within one of a complimentary pair ofexisting flow holes 26 will now be described. First, the hoist 49, asseen in FIG. 2A, is used to lower the strongback assembly 52 onto thecore barrel 14 and, in particular, to place the clamps 64a and 64b ofthe strongback assembly 52 about the flange 66. As shown in FIG. 4A, thepointer 78 is aligned with a corresponding one of the pointers 122,whereby the precise position of a complimentary pair of existing flowholes 26 is known, as shown in FIG. 3E. Next, the circumferential table136 is driven by its circumferential drive motor 140 as far right or farleft as possible, dependent upon whether a left-handed or right-handedplug 30 of the complimentary pair is to be inserted. Thereafter, each ofthe plug arm 154 and the probe arm 156 is withdrawn from the peripheralsurface of the core barrel 14. If not previously done, a probe 178 ismounted within one of the recesses 180, whereas a plug is disposedwithin a corresponding one of the recesses 184. Next, the tool carriageassembly 54 is lowered from its top-most position to a next positionaligned with the existing flow holes 26. Next, the probe arm 156carrying the probe 178 is driven toward the core barrel 14 to withinapproximately 0.125 inches. Next, the circumferential drive motor 140 isenergized to sweep the probe 178 past the corresponding existing flowhole 26. When a maximum output signal from the eddy current sensor 179eis observed on the display device 216a, the horizontal location of thehole 26 is obtained by noting the horizontal coordinate as derived fromthe output signal of the resolver 142 associated with thecircumferential drive motor 140 and displayed upon the position display212c. Next, it is necessary to recheck the vertical position of theexisting flow hole 26. In particular, the tool carriage assembly 54carrying the probe arm 156 and its probe 178 is moved vertically untilthe eddy current sensor 179e provides a maximum output signal,indicating that the probe 178 is aligned with respect to the horizontalaxis of the existing flow hole 26. Now, the output of the resolver 220associated with the cable drive motor 84, as displayed upon the display212d, is observed to obtain the vertical coordinate of the hole 26. Asexplained above, the precise diameter of the existing flow hole 26 isthen observed upon the display device 212b and, if the selected plug 30is of a corresponding diameter, the probe 178 is withdrawn, and the toolcarriage assembly 54 is lowered a distance corresponding to thatdistance between the plug arm 154 and the probe arm 156. Thereafter, theplug arm drive motor 158 is energized, whereby the plug arm 154 isdriven radially toward the core barrel 14 inserting its plug 30 withinthe aligned existing flow hole 26. The corresponding TV camera 88 isused to visually verify that the plug 30 has been inserted within itsexisting flow hole 26. Thereafter, pressure is applied to the plug 30,whereby the plug 30 is expanded fitting tightly within its existing flowhole 26. Thus, pressure is released within the hydraulic cylinder 90, asseen in FIG. 5C, whereby the slide 86 releases the plug 30, before theplug arm 154 is withdrawn and the carriage tool assembly 54 is returnedto the elevation of the work deck 44, as seen in FIG. 2A. Thereafter,the probe 178 is disposed to the other recess 180 of the probe arm 156and another plug 30 is disposed within a corresponding recess 184 of theplug arm 154. The above steps are then repeated to insert the next plug30 into the other of the complimentary existing flow holes 26.Thereafter, the strongback assembly 72 is repositioned so that itsindicator 78 is aligned to the next pointer 122 and the next set ofplugs 30 are inserted.

In considering this invention, it should be remembered that the presentdisclosure is illustrative only and the scope of the invention should bedetermined by the appended claims.

We claim:
 1. Support apparatus for supporting and selectively locating atool with respect to its work piece, the work piece having first andsecond dimensions, said support apparatus comprising:(a) a tool carriagefor receiving the tool; (b) a support structure for supporting andguiding said tool carriage with respect to the workpiece; (c) firstdrive means mounted on said support structure and coupled to said toolcarriage for selectively driving said tool carriage along said firstdimension; (d) rail means mounted on said tool carriage along saidsecond dimension; (e) a support table mounted for movement along saidrail means; (f) .[.second drive means mounted on said tool carriageselectively driving the tool along said second dimension, said.]. seconddrive means mounted on said support table and engaging said toolcarriage to drive said support table along said rail means, whereby thetool may be accurately positioned with respect to the work piece; and(g) clamp means affixed to said support structure for engaging the workpiece for suspending said support structure, whereby said supportstructure extends along said first dimension of said work piece. 2.Support apparatus as claimed in claim 1, wherein said support structureincludes an indicator for aligning said support structure with respectto the workpiece. .[.3. Support apparatus as claimed in claim 1, whereinthe workpiece includes a third dimension and there is further includedthird driving means mounted on said tool carriage for selectively drivethe tool along aid third dimension with respect to the workpiece..]. 4.Support apparatus as claimed in claim 1, wherein the workpiece includesa third dimension and there is further included third drive meansmounted on said support table for driving the tool along said thirddimension with respect to the workpiece.
 5. Support apparatus as claimedin claim 4, wherein there is included a tool mounting arm affixed tosaid third drive means to be driven thereby along said third dimension.6. Support apparatus as claimed in claim 5, wherein said tool receivingarm includes means for releasably grasping the tool.
 7. Supportapparatus as claimed in claim 4, wherein the workpiece includes at leastone work surface and there is further included sensing means for sensingthe location of the work surface and fourth drive means mounted on saidsupport table for disposing said sensing means along said thirddimension with respect to the workpiece and its work surface.
 8. Supportapparatus as claimed in claim 7, wherein there is further included asensing means arm coupled to said fourth drive means for carrying saidsensing means.
 9. Support apparatus as claimed in claim 1, wherein theworkpiece includes at least one work surface and a pointer disposedthereon in a fixed relation with the work surface, and there is furtherincluded indicator means mounted upon said tool carriage to permitalignment of said support apparatus with respect to the work surface.10. Support apparatus as claimed in claim 9, wherein said second drivemeans is mounted on said .[.tool carriage.]. .Iadd.support table.Iaddend.in a fixed relationship with respect to said indicator meansfor moving the tool with respect to said indicator means as aligned withthe pointer to align the tool with respect to the work surface. 11.Support apparatus as claimed in claim 10, wherein there is includedencoder means mounted on said .[.tool carriage.]. .Iadd.support table.Iaddend.and coupled to the tool for providing an output signalindicative of the relative movement of the tool with respect to saidindicator means.
 12. Support apparatus as claimed in claim 4, whereinthere is included first encoder means mounted on said .[.tool carriageand coupled to said support table.]. .Iadd.support table and engagingsaid tool carriage .Iaddend.for providing an output signal indicative ofthe relative movement between said support table and said tool carriagealong said second dimension, and second encoder means mounted on saidsupport table and coupled to the tool for providing an output signalindicative of the movement imparted to the tool by said third drivemeans along said third dimension.
 13. In a nuclear reactor having a corebarrel of a substantially cylindrical configuration with an axis and aplurality of flow holes disposed therethrough, a remotely controlledapparatus for supporting and selectively disposing a tool with respectto the core barrel, said remotely controlled apparatus comprising:(a) atool carriage for receiving the tool; (b) a strongback assembly forsupporting and guiding said tool carriage with respect to the corebarrel; (c) clamp means affixed to said strongback assembly for engagingthe core barrel for suspending said strongback assembly along a firstdimension substantially parallel to the axis of the core barrel; (d)first drive means mounted on said strongback assembly and coupled tosaid tool carriage for selectively driving said tool carriage along saidfirst dimension; (e) a support table; (f) means mounted on said toolcarriage for supporting said support table for movement along an arcuatepath corresponding to said cylindrical configuration; and (g) seconddrive means on said .[.tool carriage.]. .Iadd.support table .Iaddend.and.[.coupled to said support table.]. .Iadd.engaging said tool carriage.Iaddend.for selectively driving said support table along said arcuatepath, whereby the tool is accurately positioned with respect to the corebarrel.
 14. The remotely controlled apparatus as claimed in claim 13,wherein there is further included third drive means mounted on saidsupport table and coupled to said tool for selectively disposing saidtool along a second dimension aligned with respect to a radius of saidcylindrical configuration, whereby said tool may be engaged with anddisengaged from said core barrel.
 15. The remotely controlled apparatusas claimed in claim 14, wherein there is included a tool mounting armaffixed to said third drive means to be driven thereby along said seconddimension.
 16. The remotely controlled apparatus as claimed in claim 15,wherein said tool mounting arm includes means for releasably grasping aplug to be selectively inserted within one of said plurality of flowholes.
 17. The remotely controlled apparatus as claimed in claim 16,wherein the workpiece includes at least one work surface and there isfurther included sensing means for sensing the location of one of saidplurality of flow holes and fourth drive means mounted on said supporttable for disposing said sensing means along said second dimension withrespect to said core barrel.
 18. The remotely controlled apparatus asclaimed in claim 17, wherein there is further included a sensing meansarm coupled to said fourth drive means for carrying said sensing means.19. The remotely controlled apparatus as claimed in claim 18, whereinsaid core barrel includes at least one pointer disposed thereon in afixed relation with corresponding of said plurality of flow holes, andthere is further included indicator means mounted upon said toolcarriage to permit alignment of said remotely controlled apparatus withrespect to said corresponding of said plurality of flow holes.
 20. Theremotely controlled apparatus as claimed in claim 19, wherein saidsecond drive means is mounted on said .[.tool carriage.]. .Iadd.supporttable .Iaddend.in a fixed relationship with respect to said indicatormeans for moving said tool with respect to said indicator means asaligned with said pointer to align said tool with respect to one of saidplurality of flow holes.
 21. The remotely controlled apparatus asclaimed in claim 20, wherein there is included encoder means mounted onsaid .[.tool carriage.]. .Iadd.support table .Iaddend.and coupled tosaid tool for providing an output signal indicative of the relativeposition of said tool with respect to said indicator means.
 22. Theremotely controlled apparatus as claimed in claim 20, wherein there isincluded first encoder means mounted on said .[.tool carriage.]..Iadd.support table .Iaddend.and coupled to said .[.support table.]..Iadd.tool carriage .Iaddend.for providing an output signal indicativeof the relative position of said support table with respect to saidindicator means, and second encoder means mounted on said support tableand coupled to said tool for providing an output signal indicative ofthe movement imparted to said tool by said third drive means along saidsecond dimension.